Our present interests are three-fold: 1) to determine whether tyrosine hydroxylase of dopamine-containing amacrine cells becomes tolerant to activation by neuroleptic drugs and to evaluate whether tolerance to neuroleptic drugs alters activation by a photic stimulus; 2) to characterize and compare the activation of retinal tyrosine hydroxylase induced in vivo by photic stimulation and in vitro by cAMP-dependent protein kinase; and 3) to investigate some of the properties of the epinephrine-containing system of retina.